Inspiration from physics for thinking about economics, finance and social systems

Monday, September 26, 2011

Overconfidence is adaptive?

A fascinating paper in Nature from last week suggests that overconfidence may actually be an adaptive trait. This is interesting as it strikes at one of the most pervasive assumptions in all of economics -- the idea of human rationality, and the conviction that being rational must always be more adaptive than being irrational. Quite possibly not:

Humans show many psychological biases, but one of the most consistent, powerful and widespread is overconfidence. Most people show a bias towards exaggerated personal qualities and capabilities, an illusion of control over events, and invulnerability to risk (three phenomena collectively known as ‘positive illusions’)2, 3, 4, 14. Overconfidence amounts to an ‘error’ of judgement or decision-making, because it leads to overestimating one’s capabilities and/or underestimating an opponent, the difficulty of a task, or possible risks. It is therefore no surprise that overconfidence has been blamed throughout history for high-profile disasters such as the First World War, the Vietnam war, the war in Iraq, the 2008 financial crisis and the ill-preparedness for environmental phenomena such as Hurricane Katrina and climate change9, 12, 13, 15, 16.

If overconfidence is both a widespread feature of human psychology and causes costly mistakes, we are faced with an evolutionary puzzle as to why humans should have evolved or maintained such an apparently damaging bias. One possible solution is that overconfidence can actually be advantageous on average (even if costly at times), because it boosts ambition, morale, resolve, persistence or the credibility of bluffing. If such features increased net payoffs in competition or conflict over the course of human evolutionary history, then overconfidence may have been favoured by natural selection5, 6, 7, 8.

However, it is unclear whether such a bias can evolve in realistic competition with alternative strategies. The null hypothesis is that biases would die out, because they lead to faulty assessments and suboptimal behaviour. In fact, a large class of economic models depend on the assumption that biases in beliefs do not exist17. Underlying this assumption is the idea that there must be some evolutionary or learning process that causes individuals with correct beliefs to be rewarded (and thus to spread at the expense of individuals with incorrect beliefs). However, unbiased decisions are not necessarily the best strategy for maximizing benefits over costs, especially under conditions of competition, uncertainty and asymmetric costs of different types of error8, 18, 19, 20, 21. Whereas economists tend to posit the notion of human brains as general-purpose utility maximizing machines that evaluate the costs, benefits and probabilities of different options on a case-by-case basis, natural selection may have favoured the development of simple heuristic biases (such as overconfidence) in a given domain because they were more economical, available or faster.

The paper studies this question in a simple analytical model of an evolutionary environment in which individuals compete for resources. If the resources are sufficiently valuable, the authors find, overconfidence can indeed be adaptive:

Here we present a model showing that, under plausible conditions for the value of rewards, the cost of conflict, and uncertainty about the capability of competitors, there can be material rewards for holding incorrect beliefs about one’s own capability. These adaptive advantages of overconfidence may explain its emergence and spread in humans, other animals or indeed any interacting entities, whether by a process of trial and error, imitation, learning or selection. The situation we model—a competition for resources—is simple but general, thereby capturing the essence of a broad range of competitive interactions including animal conflict, strategic decision-making, market competition, litigation, finance and war.

Very interesting. But I just had a thought -- perhaps this may also explain why many economists seem to exhibit such irrational exuberance over the value of neo-classical theory itself?

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Physicist and science writer. I was formerly an editor with the international science journal Nature and also the magazine New Scientist. I am the author of three earlier books, and have written extensively for publications including Nature, Science, the New York Times, Wired and the Harvard Business Review. I currently write monthly columns for Nature Physics and for Bloomberg Views.